If your need is that great & the tablet is usable & compatible I've seen wireless keyboard/mouse combos online for under $50 [both USD & CAD]. I'm not aware of any hardware manufacturer which offers more than a one-year warranty – some are only 90 days.
However, I don't see the correlation between a failed piece of hardware & the reference to one-time-purchase v. subscription software. Microsoft Office 2024 is a one-time-purchase product separate from Microsoft 365 Subscription. IMO, however, the subscription plan has numerous advantages & costs considerably less in the long run, especially since it can be paid monthly. Whether we like it or not that is the direction the industry on the whole has taken... some developers offer only subscription plans.